What is the Beaufort Scale?

The Beaufort Scale, used throughout the marine world, has developed over
many years since it was first devised by Admiral Francis Beaufort in 1806.
Today, the Beaufort scale is defined for seamen in terms of sea state.
It's emphasis is more on the observed effect of the wind, rather than the
actual wind speed.

Admiral Francis Beaufort

Francis Beaufort was born in 1774 in County Meath, Ireland and began his
nautical career at 13 as a cabin boy in the Navy. He realised that it was
important whilst at sea to be aware of, and to know about weather
conditions, so started to keep a meteorological journal, which he continued
to do until he died.

By the age of 22 Beaufort had risen to the position of lieutenant. Whilst
on assignment in 1812, which was a combined hydro graphic study and patrol
mission against the pirates operating out of the Levant, the mission came
under attack and Beaufort got hit in the groin by sniper fire, leaving him
with a fractured hip. His ship was called back and Beaufort's Navy career
changed direction at this point. He was given the position of Hydrographer
to the Admiralty, and never returned to the sea. Beaufort rose to the
position of Rear Admiral, and worked in the Navy until two years before his
death in 1857, serving for 68 years.

Beaufort invented the Beaufort Scale in 1806, and used it from then
onwards. The Royal Navy then adopted his method in 1838. Although over the
next hundred years the Beaufort scale was
slightly adapted, it is still based around Francis Beaufort's original
concept.

The Beaufort Wind Scale

Table of Beaufort wind force in terms of observed sea state

Beaufort Force

Wind Speed Knots

Description

Sea Condition

0

0

Calm

Sea like a mirror

1

1 - 3

Light air

Ripples but without foam crests

2

4 - 6

Light breeze

Small wavelets. Crests do not break

3

7 - 10

Gentle breeze

Large wavelets. Perhaps scattered white horses

4

11 - 16

Moderate breeze

Small waves. Fairly frequent white horses

5

17 - 21

Fresh breeze

Moderate waves. Many white horses

6

22 - 27

Strong breeze

Large waves begin to form; white foam crests. Probably spray

7

28 - 33

Near gale

Sea heaps up and white foam blown in streaks along the direction of the wind

8

34 - 40

Gale

Moderately high waves. Crests begin to break into spindrift. The foam is blown in well marked streaks along the direction of the wind

9

41 - 47

Severe gale

High waves. Dense foam along the direction of the wind. Crests of waves begin to roll over. Spray may affect visibility

10

48 - 55

Storm

Very high waves with long overhanging crests. The surface of the sea takes a white appearance. The tumbling of the sea becomes heavy and shock-like. Visibility affected

11

56 - 63

Violent storm

Exceptionally high waves. The sea is completely covered with long white patches of foam lying in the direction of the wind. Visibility affected

12

64+

Hurricane

The air is filled with foam and spray. Sea completely white with driving spray. Visibility very seriously affected